To quote: Beta9 would have been out a few days ago, but then Nintendo came up with the new October 23 update with perfect timing, so we had to make sure the beta9 installer was compatible (read: exploited a new bug nobody knew about until then).

Warning: We've updated the ELF loader to be compliant with the specs. Unfortunately, DevkitPPC ELFs currently are not (they will be in the next release), so they'll break. App authors should distribute DOL versions. If they don't, tell them to. If they don't, convert it yourself:

powerpc-gekko-objcopy -O binary boot.elf boot.dol

Newer ELFs produced by the new toolchain (when it comes out, hopefully soon) will be compatible both with the new loaders (HBC beta9) and all the old loaders. All DOL files work as usual. The new linkerscript will also be more flexible (we're using it for all the binaries involved in HBC, instead of a mixture of custom linker scripts). Authors of other loaders will like this.

We're keeping the new bug under wraps for now to increase the chances of us being able to use it for the BootMii-Core installer too

Even with beta9, I don't recommend that you update unless you need to. You can use Muzer's or tona's installer to install IOS51 and the new Wii Shop only, which will keep all the old vulnerable IOSes too.